Precisely controlled milliwatt levels of CO2 laser energy can fuse the protein-collagen matrix of tissues. The following proposal is designed to test the hypothesis that this method of tissue fusion used for vascular repair may provide better anatomic and functional results compared to conventional hand-sewn controls. The technical problems and functional alterations of conventional vascular repair methods of small vessels are well recognized: narrowing of the lumen, intimal tears, and stimulation of smooth muscle cells from repetitive transmural suture placement, leading to early thrombosis or prolonged functional alterations. The milliwatt CO2 laser may provide a useful method of tissue fusion because its energy is absorbed in a chromagen-independent uniform manner with a shallow depth of penetration. This study will evaluate the application of milliwatt CO2 laser tissue fusion techniques to the carotid artery and aorta of the rabbit. Methods, laser power, power densities, and energy fluence levels necessary to fuse the protein-collagen matrix of the media and adventitia will be established. Strength of the tissue fusion bond will be determined by slowly raising peak systolic pressures wih an epinephrine infusion to the point of anastomotic disruption or a maximum pressure of 300 mm Hg. Patency and anastomotic morphology in both the laser fused and hand sewn vessels will be evaluated non-invasively with B-Mode ultrasonic imaging. The nature of the laser-induced injury and the pattern of healing will be analyzed with sequential histology and scanning and transmission electron microscopy and compared to that generated by conventional transmural suture technique. These studies will provide a technical and functional analysis of the laser-created tissue fusion vascular anastomosis. The establishment of a method of tissue repair, particularly one which can be used for small vessel anastomosis and minimize disruption of the endothelial flow surface, may permit improved immediate technical results and less distortion of the blood-vessel wall interaction.